A number of products are commonly sold in bags, usually of paper, with a closure at their upper end. In many cases, where the contents of the package are used gradually and may deteriorate if exposed to the atmosphere for prolonged periods, it is desirable to make provision for reclosure of the package once opened. A number of proposals have been made for reclosable bags of one sort or another, the most widely used package of this type having a tin tie attached to one edge of the open top end of the bag, which may be closed and reclosed by repeatedly folding the bag end and securing the folds with the tin tie. This form of package has several disadvantages. Firstly, original closure of the packages must either be carried out manually, which is slow and labour intensive, or by the use of very expensive and complicated machinery. Secondly, the tin ties have a metal content, which may interfere with the operation of metal detectors used to detect foreign bodies in the product being packaged and is objectionable if the paper of the bag is incinerated or recycled. Thirdly, reclosure of the package requires a certain amount of care if it is to be effective. Although the tin tie can be applied to the bag automatically during manufacture, and the bags can then be closed automatically, such automation is complex and expensive, and is not economically feasible in many instances. Additionally, the tin tie adds significantly to the cost of the bag.
An example of a bag incorporating a tin tie is shown in U.S. Pat. No. 3,545,668 (Hultberg), which is cited as exemplary of prior art relating to tin tie bags.
Various attempts have been made to find alternatives to the use of tin ties in a reclosable package. One time-honoured approach is to use a separable clip to hold the folded top of the bag closed, an example of such a closure being shown in U.S. Pat. No. 3,680,771 (Blunston). Such clips have the disadvantage of being expensive, separable from the container and therefore subject to loss, and are also in general only easily applied to containers made from fairly stiff material.
Various proposals have been made for th use of non-setting adhesives to produce reclosable packages. U.S. Pat. No. 3,212,698 (Balcom) shows a bag with an adhesive sealing tab and a further non-setting adhesive coating to render the bag reclosable. Other proposals, such as that contained in U.S. Pat. No. 4,066,167 (Hanna et al), have provided a sealing strip attached to the bag which may be used to reseal the container after its original seal has been broken or removed. This of course complicates manufacture of the bag, and is rather clumsy in use since it requires the user to recover the strip from the bag and then apply it.
A further problem in the use of adhesive tape for sealing such bags is that, without tedious multiple folding of the top of the bag, it is difficult to produce a reasonably air-tight seal. U.S. Pat. No. 3,396,902 shows how the top of a bag may be specially shaped so as to ensure that a sealing strip does provide a good seal, but this proposal requires a special configuration of the top of the bag to ensure that all of the bag surfaces are exposed to the sealing strip.
A further feature which it is difficult to incorporate into known forms of bag is the distribution of promotional material such as coupons, or the application of other information which requres to be applied at the time of packaging, such as packaging or expiry dates. U.S. Pat. No. 3,439,866 (Kuhnle) discloses a bag closure arrangement in which a coupon or other material is folded into the neck of the bag during closure, for which purpose pressure sensitive adhesive may be utilized. A disadvantage of this arrangement is that the coupon must be inserted as a separate step, the coupon is not visible until the package is opened, and the closure methods described fall in the categories already discussed above. The Kuhnle arrangement does not provide any solution to the problem of applying packaging and like dates or codes, which hitherto have required the use of an additional printing or labelling step.